FIG. 25 is a drawing showing a friction stir welding apparatus 1 of the conventional art. The friction stir welding apparatus 1 includes a welding device 2 performing a welding operation and an arm 3 connected to the welding device 2 for positioning the welding device 2 for an object 4 to be welded. The welding device 2 is equipped with a tool holding jig 7 installed rotatably about a reference axis L1 and movably along the reference axis L1, a rotation motor for rotating the tool holding jig 7, and a displacement motor for moving the tool holding jig 7 along the reference axis L1. On the tool holding jig 7, a columnar welding tool 5 is mounted. The arm 3 may be made by a multi-joint robot and a tip 6 of the arm 3 is connected to the welding device 2.
The conventional friction stir welding apparatus 1 moves the welding device 2 toward the object 4 by the arm 3. Next, the apparatus 1 operates the welding tool 5 mounted to the tool holding jig 7 to rotate and make contact with the object 4. By doing this, frictional heat is generated in the object 4. The friction stir welding apparatus 1 makes the object 4 fluid by the frictional heat, stirs the object 4, and mixes and welds the boundary parts of two members 4a and 4b constituting the object 4 to be welded.
The aforementioned welding method using frictional heat is called friction stir welding (abbreviated to “FSW”).
Conventionally, an object to be welded by the friction stir welding is a large object. Therefore, without moving a large object 4, it is welded by moving the welding device 2 by the arm 3.
The welding device 2 includes a rotation motor and a pressure motor. Therefore, the weight thereof is large such as about 120 kg. The arm 3 must be highly rigid in order to support the welding device 2. Further, when the moving distance of the welding device 2 is long, the arm 3 must be long. As mentioned above, in the friction stir welding apparatus 1, it is required to make the arm long and highly rigid, thus the necessary space occupied by the arm 3 is wider than that occupied by the welding device 2. Therefore, a problem arises that the structure becomes inevitably large. Further, in the friction stir welding apparatus 1, a moving space for the welding device 2 to move to the object 4 is required, so that a problem arises that a sufficiently large space for installation is necessary.
Further, the whole structure of the friction stir welding apparatus is complicated due to the arm 3, thereby, a problem arises that the maintenance and adjustment are difficult. Further, according to the shape of the object 4, an operator should perform both the teaching operation and the exchange operation of a welding tool, thereby, a problem arises that the workability is lowered.
Therefore, the present invention is intended to provide a friction stir welding apparatus which has a simple constitution and a good operability, and can be miniaturized.